Flashing is widely employed in the building industry to weatherproof building roof constructions at their various juncture points with other components, such as vertical walls, and around roof penetrations, such as pipes, support beams, support rods, and the like, which extend through the roof.
Flashing for pipes and other roof penetrations typically are composed of thin sheet metal, which is cut and formed into the desired shape by construction workers at the building site, and fitted about the roof penetration to seal the opening of the roof between the penetration and the roof. For flat roofs, the flashing typically may consist of a base plate of sheet metal having a central opening. The base plate lies flat on and surrounds the opening in the roof. An upstanding, cylindrical hollow sleeve, or stack, surrounds the base plate opening, is secured thereto, and projects upwardly a distance above the roof line in surrounding relation to the pipe penetrating the roof. The stack is spaced outwardly from the pipe penetration a sufficient distance to permit relative movement between the penetration and roof construction. A cap, or counter flashing, is mounted in water-tight surrounding relation on the roof penetration, and overlies the upper end of the flashing stack to provide a weatherproof cover for the upper end of the stack.
Generally, in such sheet metal flashing constructions, the base plate is split to its central opening to facilitate its placement about the roof penetration, and the stack of the flashing is formed of a single flexible sheet of metal which is bent around the roof penetration into a cylindrical shape and soldered along its longitudinal seam to seal the same. The lower end of the stack is soldered to base plate and tabs located around its central opening. The counterflashing, or cap, of the flashing unit is generally a longitudinally split hollow sleeve of sheet metal of larger diameter than the stack, and is opened to encircle the protrusion and the upper end of the flashing stack. The counter flashing is secured to the roof penetration by suitable means, such as an internal gasket, sealant, and clamps.
In fabricating sheet metal flashings on site, even though architecturally specified, construction workers often may be inexperienced in properly sizing, cutting, and shaping the sheet metal stock material to the proper dimensions to effectively seal piping and other penetrations through the roof of the building. In addition, on-site flashing construction and fabrication results in increased labor and time for construction personnel.
It is also known to employ prefabricated flashing units made of a rigid plastic with an elastomeric covering material. One such prefabricated flashing unit is disclosed in U. S. Pat. No. 4,211,423, and consists of a multipart generally cylindrical unit with base flange and boot or cap of varying diameter stack, which may be height cut to provide a desired diameter to accommodate pipe of corresponding diameter. As disclosed in the patent, the roof seal device appears to be composed of multiple inner and outer sections which must be precisely aligned and secured with clamps and adhesively sealed at overlapping elastomeric portions resulting in what would appear to be a labor-intensive installation.
Prefabricated plastic flashings are also known which consist of a flexible longitudinally split generally cylindrical sleeve which is distorted to be brought around a roof penetration and thereafter secured along the split by screws and suitable clamping means.
It is generally believed that plastic and rubber flashing units have less resistance to UV light and weathering during use, and do not have the durability and use life of the sheet metal flashings.